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gcc/libstdc++-v3/include/bits/iterator_concepts.h
Jonathan Wakely d37303d15a libstdc++: remove redundant equality operators 
Now that operator<=> is supported, these operators can be generated by
the compiler.

	* include/bits/iterator_concepts.h (unreachable_sentinel_t): Remove
	redundant equality operators.
	* testsuite/util/testsuite_iterators.h (test_range::sentinel):
	Likewise.

From-SVN: r277888
2019-11-06 17:53:12 +00:00

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// Concepts and traits for use with iterators -*- C++ -*-
// Copyright (C) 2019 Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library. This library is free
// software; you can redistribute it and/or modify it under the
// terms of the GNU General Public License as published by the
// Free Software Foundation; either version 3, or (at your option)
// any later version.
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
// Under Section 7 of GPL version 3, you are granted additional
// permissions described in the GCC Runtime Library Exception, version
// 3.1, as published by the Free Software Foundation.
// You should have received a copy of the GNU General Public License and
// a copy of the GCC Runtime Library Exception along with this program;
// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
// <http://www.gnu.org/licenses/>.
/** @file bits/iterator_concepts.h
* This is an internal header file, included by other library headers.
* Do not attempt to use it directly. @headername{iterator}
*/
#ifndef _ITERATOR_CONCEPTS_H
#define _ITERATOR_CONCEPTS_H 1
#pragma GCC system_header
#include <concepts>
#include <bits/ptr_traits.h> // to_address
#include <bits/range_cmp.h> // identity, ranges::less
#if __cpp_lib_concepts
namespace std _GLIBCXX_VISIBILITY(default)
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION
struct input_iterator_tag;
struct output_iterator_tag;
struct forward_iterator_tag;
struct bidirectional_iterator_tag;
struct random_access_iterator_tag;
struct contiguous_iterator_tag;
template<typename _Iterator>
struct iterator_traits;
template<typename _Tp> requires is_object_v<_Tp>
struct iterator_traits<_Tp*>;
template<typename _Iterator, typename>
struct __iterator_traits;
namespace __detail
{
template<typename _Tp>
using __with_ref = _Tp&;
template<typename _Tp>
concept __can_reference = requires { typename __with_ref<_Tp>; };
template<typename _Tp>
concept __dereferenceable = requires(_Tp& __t)
{
{ *__t } -> __can_reference;
};
// FIXME: needed due to PR c++/67704
template<__detail::__dereferenceable _Tp>
struct __iter_ref
{
using type = decltype(*std::declval<_Tp&>());
};
} // namespace __detail
template<typename _Tp>
using iter_reference_t = typename __detail::__iter_ref<_Tp>::type;
namespace ranges
{
namespace __cust_imove
{
template<typename _Tp>
concept __adl_imove
= (std::__detail::__class_or_enum<remove_reference_t<_Tp>>)
&& requires(_Tp&& __t) { iter_move(static_cast<_Tp&&>(__t)); };
struct _IMove
{
private:
template<typename _Tp>
static constexpr bool
_S_noexcept()
{
if constexpr (__adl_imove<_Tp>)
return noexcept(iter_move(std::declval<_Tp>()));
else
return noexcept(*std::declval<_Tp>());
}
public:
template<typename _Tp>
requires __adl_imove<_Tp> || requires(_Tp& __e) { *__e; }
constexpr decltype(auto)
operator()(_Tp&& __e) const
noexcept(_S_noexcept<_Tp>())
{
if constexpr (__adl_imove<_Tp>)
return iter_move(static_cast<_Tp&&>(__e));
else if constexpr (is_reference_v<iter_reference_t<_Tp>>)
return std::move(*__e);
else
return *__e;
}
};
} // namespace __cust_imove
inline namespace __cust
{
inline constexpr __cust_imove::_IMove iter_move{};
} // inline namespace __cust
} // namespace ranges
namespace __detail
{
// FIXME: needed due to PR c++/67704
template<__detail::__dereferenceable _Tp>
struct __iter_rvalue_ref
{ };
template<__detail::__dereferenceable _Tp>
requires requires(_Tp& __t)
{
{ ranges::iter_move(__t) } -> __detail::__can_reference;
}
struct __iter_rvalue_ref<_Tp>
{ using type = decltype(ranges::iter_move(std::declval<_Tp&>())); };
} // namespace __detail
template<typename _Tp>
using iter_rvalue_reference_t
= typename __detail::__iter_rvalue_ref<_Tp>::type;
template<typename> struct incrementable_traits { };
template<typename _Tp> requires is_object_v<_Tp>
struct incrementable_traits<_Tp*>
{ using difference_type = ptrdiff_t; };
template<typename _Iter>
struct incrementable_traits<const _Iter>
: incrementable_traits<_Iter> { };
template<typename _Tp> requires requires { typename _Tp::difference_type; }
struct incrementable_traits<_Tp>
{ using difference_type = typename _Tp::difference_type; };
template<typename _Tp>
requires (!requires { typename _Tp::difference_type; }
&& requires(const _Tp& __a, const _Tp& __b)
{
requires (!is_void_v<remove_pointer_t<_Tp>>); // PR c++/78173
{ __a - __b } -> integral;
})
struct incrementable_traits<_Tp>
{
using difference_type
= make_signed_t<decltype(std::declval<_Tp>() - std::declval<_Tp>())>;
};
namespace __detail
{
// An iterator such that iterator_traits<_Iter> names a specialization
// generated from the primary template.
template<typename _Iter>
concept __primary_traits_iter
= __is_base_of(__iterator_traits<_Iter, void>, iterator_traits<_Iter>);
template<typename _Iter, typename _Tp>
struct __iter_traits_impl
{ using type = iterator_traits<_Iter>; };
template<typename _Iter, typename _Tp>
requires __primary_traits_iter<_Iter>
struct __iter_traits_impl<_Iter, _Tp>
{ using type = _Tp; };
// ITER_TRAITS
template<typename _Iter, typename _Tp = _Iter>
using __iter_traits = typename __iter_traits_impl<_Iter, _Tp>::type;
} // namespace __detail
template<typename _Tp>
using iter_difference_t = typename
__detail::__iter_traits<_Tp, incrementable_traits<_Tp>>::difference_type;
namespace __detail
{
template<typename> struct __cond_value_type { };
template<typename _Tp> requires is_object_v<_Tp>
struct __cond_value_type<_Tp>
{ using value_type = remove_cv_t<_Tp>; };
} // namespace __detail
template<typename> struct readable_traits { };
template<typename _Tp>
struct readable_traits<_Tp*>
: __detail::__cond_value_type<_Tp>
{ };
template<typename _Iter> requires is_array_v<_Iter>
struct readable_traits<_Iter>
{ using value_type = remove_cv_t<remove_extent_t<_Iter>>; };
template<typename _Iter>
struct readable_traits<const _Iter>
: readable_traits<_Iter>
{ };
template<typename _Tp> requires requires { typename _Tp::value_type; }
struct readable_traits<_Tp>
: __detail::__cond_value_type<typename _Tp::value_type>
{ };
template<typename _Tp> requires requires { typename _Tp::element_type; }
struct readable_traits<_Tp>
: __detail::__cond_value_type<typename _Tp::element_type>
{ };
template<typename _Tp>
using iter_value_t = typename
__detail::__iter_traits<_Tp, readable_traits<_Tp>>::value_type;
namespace __detail
{
template<typename _Iter>
concept __cpp17_iterator = copyable<_Iter>
&& requires(_Iter __it)
{
{ *__it } -> __can_reference;
{ ++__it } -> same_as<_Iter&>;
{ *__it++ } -> __can_reference;
};
template<typename _Iter>
concept __cpp17_input_iterator = __cpp17_iterator<_Iter>
&& equality_comparable<_Iter>
&& requires(_Iter __it)
{
typename incrementable_traits<_Iter>::difference_type;
typename readable_traits<_Iter>::value_type;
typename common_reference_t<iter_reference_t<_Iter>&&,
typename readable_traits<_Iter>::value_type&>;
typename common_reference_t<decltype(*__it++)&&,
typename readable_traits<_Iter>::value_type&>;
requires signed_integral<typename incrementable_traits<_Iter>::difference_type>;
};
template<typename _Iter>
concept __cpp17_fwd_iterator = __cpp17_input_iterator<_Iter>
&& constructible_from<_Iter>
&& is_lvalue_reference_v<iter_reference_t<_Iter>>
&& same_as<remove_cvref_t<iter_reference_t<_Iter>>,
typename readable_traits<_Iter>::value_type>
&& requires(_Iter __it)
{
{ __it++ } -> convertible_to<const _Iter&>;
{ *__it++ } -> same_as<iter_reference_t<_Iter>>;
};
template<typename _Iter>
concept __cpp17_bidi_iterator = __cpp17_fwd_iterator<_Iter>
&& requires(_Iter __it)
{
{ --__it } -> same_as<_Iter&>;
{ __it-- } -> convertible_to<const _Iter&>;
{ *__it-- } -> same_as<iter_reference_t<_Iter>>;
};
template<typename _Iter>
concept __cpp17_randacc_iterator = __cpp17_bidi_iterator<_Iter>
&& totally_ordered<_Iter>
&& requires(_Iter __it,
typename incrementable_traits<_Iter>::difference_type __n)
{
{ __it += __n } -> same_as<_Iter&>;
{ __it -= __n } -> same_as<_Iter&>;
{ __it + __n } -> same_as<_Iter>;
{ __n + __it } -> same_as<_Iter>;
{ __it - __n } -> same_as<_Iter>;
{ __it - __it } -> same_as<decltype(__n)>;
{ __it[__n] } -> convertible_to<iter_reference_t<_Iter>>;
};
template<typename _Iter>
concept __iter_with_nested_types = requires {
typename _Iter::iterator_category;
typename _Iter::value_type;
typename _Iter::difference_type;
typename _Iter::reference;
};
template<typename _Iter>
concept __iter_without_nested_types = !__iter_with_nested_types<_Iter>;
template<typename _Iter, bool __use_arrow = false>
struct __ptr
{ using type = void; };
template<typename _Iter> requires requires { typename _Iter::pointer; }
struct __ptr<_Iter, true>
{ using type = typename _Iter::pointer; };
template<typename _Iter> requires requires { typename _Iter::pointer; }
struct __ptr<_Iter, false>
{ using type = typename _Iter::pointer; };
template<typename _Iter>
requires (!requires { typename _Iter::pointer; }
&& requires(_Iter& __it) { __it.operator->(); })
struct __ptr<_Iter, true>
{ using type = decltype(std::declval<_Iter&>().operator->()); };
template<typename _Iter>
struct __ref
{ using type = iter_reference_t<_Iter>; };
template<typename _Iter> requires requires { typename _Iter::reference; }
struct __ref<_Iter>
{ using type = typename _Iter::reference; };
template<typename _Iter>
struct __cat
{ using type = input_iterator_tag; };
template<typename _Iter>
requires requires { typename _Iter::iterator_category; }
struct __cat<_Iter>
{ using type = typename _Iter::iterator_category; };
template<typename _Iter>
requires (!requires { typename _Iter::iterator_category; }
&& __detail::__cpp17_randacc_iterator<_Iter>)
struct __cat<_Iter>
{ using type = random_access_iterator_tag; };
template<typename _Iter>
requires (!requires { typename _Iter::iterator_category; }
&& __detail::__cpp17_bidi_iterator<_Iter>)
struct __cat<_Iter>
{ using type = bidirectional_iterator_tag; };
template<typename _Iter>
requires (!requires { typename _Iter::iterator_category; }
&& __detail::__cpp17_fwd_iterator<_Iter>)
struct __cat<_Iter>
{ using type = forward_iterator_tag; };
template<typename _Iter>
struct __diff
{ using type = void; };
template<typename _Iter>
requires requires {
typename incrementable_traits<_Iter>::difference_type;
}
struct __diff<_Iter>
{
using type = typename incrementable_traits<_Iter>::difference_type;
};
} // namespace __detail
template<typename _Iterator>
requires __detail::__iter_with_nested_types<_Iterator>
struct __iterator_traits<_Iterator, void>
{
using iterator_category = typename _Iterator::iterator_category;
using value_type = typename _Iterator::value_type;
using difference_type = typename _Iterator::difference_type;
using pointer = typename __detail::__ptr<_Iterator>::type;
using reference = typename _Iterator::reference;
};
template<typename _Iterator>
requires __detail::__iter_without_nested_types<_Iterator>
&& __detail::__cpp17_input_iterator<_Iterator>
struct __iterator_traits<_Iterator, void>
{
using iterator_category = typename __detail::__cat<_Iterator>::type;
using value_type
= typename readable_traits<_Iterator>::value_type;
using difference_type
= typename incrementable_traits<_Iterator>::difference_type;
using pointer = typename __detail::__ptr<_Iterator, true>::type;
using reference = typename __detail::__ref<_Iterator>::type;
};
template<typename _Iterator>
requires __detail::__iter_without_nested_types<_Iterator>
&& __detail::__cpp17_iterator<_Iterator>
struct __iterator_traits<_Iterator, void>
{
using iterator_category = output_iterator_tag;
using value_type = void;
using difference_type = typename __detail::__diff<_Iterator>::type;
using pointer = void;
using reference = void;
};
namespace __detail
{
template<typename _Iter>
struct __iter_concept_impl
{ };
template<typename _Iter>
requires requires { typename __iter_traits<_Iter>::iterator_concept; }
struct __iter_concept_impl<_Iter>
{ using type = typename __iter_traits<_Iter>::iterator_concept; };
template<typename _Iter>
requires (!requires { typename __iter_traits<_Iter>::iterator_concept; }
&& requires { typename __iter_traits<_Iter>::iterator_category; })
struct __iter_concept_impl<_Iter>
{ using type = typename __iter_traits<_Iter>::iterator_category; };
template<typename _Iter>
requires (!requires { typename __iter_traits<_Iter>::iterator_concept; }
&& !requires { typename __iter_traits<_Iter>::iterator_category; }
&& __primary_traits_iter<_Iter>)
struct __iter_concept_impl<_Iter>
{ using type = random_access_iterator_tag; };
// ITER_TRAITS
template<typename _Iter>
using __iter_concept = typename __iter_concept_impl<_Iter>::type;
} // namespace __detail
/// Requirements for types that are readable by applying operator*.
template<typename _In>
concept readable = requires
{
typename iter_value_t<_In>;
typename iter_reference_t<_In>;
typename iter_rvalue_reference_t<_In>;
}
&& common_reference_with<iter_reference_t<_In>&&, iter_value_t<_In>&>
&& common_reference_with<iter_reference_t<_In>&&,
iter_rvalue_reference_t<_In>&&>
&& common_reference_with<iter_rvalue_reference_t<_In>&&,
const iter_value_t<_In>&>;
namespace __detail
{
// FIXME: needed due to PR c++/67704
template<readable _Tp>
struct __iter_common_ref
: common_reference<iter_reference_t<_Tp>, iter_value_t<_Tp>&>
{ };
// FIXME: needed due to PR c++/67704
template<typename _Fn, typename... _Is>
struct __indirect_result
{ };
template<typename _Fn, typename... _Is>
requires (readable<_Is> && ...)
&& invocable<_Fn, iter_reference_t<_Is>...>
struct __indirect_result<_Fn, _Is...>
: invoke_result<_Fn, iter_reference_t<_Is>...>
{ };
} // namespace __detail
template<typename _Tp>
using iter_common_reference_t
= typename __detail::__iter_common_ref<_Tp>::type;
/// Requirements for writing a value into an iterator's referenced object.
template<typename _Out, typename _Tp>
concept writable = requires(_Out&& __o, _Tp&& __t)
{
*__o = std::forward<_Tp>(__t);
*std::forward<_Out>(__o) = std::forward<_Tp>(__t);
const_cast<const iter_reference_t<_Out>&&>(*__o)
= std::forward<_Tp>(__t);
const_cast<const iter_reference_t<_Out>&&>(*std::forward<_Out>(__o))
= std::forward<_Tp>(__t);
};
/// Requirements on types that can be incremented with ++.
template<typename _Iter>
concept weakly_incrementable = default_constructible<_Iter>
&& movable<_Iter>
&& requires(_Iter __i)
{
typename iter_difference_t<_Iter>;
requires signed_integral<iter_difference_t<_Iter>>;
{ ++__i } -> same_as<_Iter&>;
__i++;
};
template<typename _Iter>
concept incrementable = regular<_Iter> && weakly_incrementable<_Iter>
&& requires(_Iter __i) { { __i++ } -> same_as<_Iter>; };
template<typename _Iter>
concept input_or_output_iterator
= requires(_Iter __i) { { *__i } -> __detail::__can_reference; }
&& weakly_incrementable<_Iter>;
template<typename _Sent, typename _Iter>
concept sentinel_for = semiregular<_Sent>
&& input_or_output_iterator<_Iter>
&& __detail::__weakly_eq_cmp_with<_Sent, _Iter>;
template<typename _Sent, typename _Iter>
inline constexpr bool disable_sized_sentinel = false;
template<typename _Sent, typename _Iter>
concept sized_sentinel_for = sentinel_for<_Sent, _Iter>
&& !disable_sized_sentinel<remove_cv_t<_Sent>, remove_cv_t<_Iter>>
&& requires(const _Iter& __i, const _Sent& __s)
{
{ __s - __i } -> same_as<iter_difference_t<_Iter>>;
{ __i - __s } -> same_as<iter_difference_t<_Iter>>;
};
template<typename _Iter>
concept input_iterator = input_or_output_iterator<_Iter>
&& readable<_Iter>
&& requires { typename __detail::__iter_concept<_Iter>; }
&& derived_from<__detail::__iter_concept<_Iter>, input_iterator_tag>;
template<typename _Iter, typename _Tp>
concept output_iterator = input_or_output_iterator<_Iter>
&& writable<_Iter, _Tp>
&& requires(_Iter __i, _Tp&& __t) { *__i++ = std::forward<_Tp>(__t); };
template<typename _Iter>
concept forward_iterator = input_iterator<_Iter>
&& derived_from<__detail::__iter_concept<_Iter>, forward_iterator_tag>
&& incrementable<_Iter> && sentinel_for<_Iter, _Iter>;
template<typename _Iter>
concept bidirectional_iterator = forward_iterator<_Iter>
&& derived_from<__detail::__iter_concept<_Iter>,
bidirectional_iterator_tag>
&& requires(_Iter __i)
{
{ --__i } -> same_as<_Iter&>;
{ __i-- } -> same_as<_Iter>;
};
template<typename _Iter>
concept random_access_iterator = bidirectional_iterator<_Iter>
&& derived_from<__detail::__iter_concept<_Iter>,
random_access_iterator_tag>
&& totally_ordered<_Iter> && sized_sentinel_for<_Iter, _Iter>
&& requires(_Iter __i, const _Iter __j,
const iter_difference_t<_Iter> __n)
{
{ __i += __n } -> same_as<_Iter&>;
{ __j + __n } -> same_as<_Iter>;
{ __n + __j } -> same_as<_Iter>;
{ __i -= __n } -> same_as<_Iter&>;
{ __j - __n } -> same_as<_Iter>;
{ __j[__n] } -> same_as<iter_reference_t<_Iter>>;
};
template<typename _Iter>
concept contiguous_iterator = random_access_iterator<_Iter>
&& derived_from<__detail::__iter_concept<_Iter>, contiguous_iterator_tag>
&& is_lvalue_reference_v<iter_reference_t<_Iter>>
&& same_as<iter_value_t<_Iter>, remove_cvref_t<iter_reference_t<_Iter>>>
&& requires(const _Iter& __i)
{
{ std::to_address(__i) }
-> same_as<add_pointer_t<iter_reference_t<_Iter>>>;
};
// [indirectcallable], indirect callable requirements
// [indirectcallable.indirectinvocable], indirect callables
template<typename _Fn, typename _Iter>
concept indirectly_unary_invocable = readable<_Iter>
&& copy_constructible<_Fn> && invocable<_Fn&, iter_value_t<_Iter>&>
&& invocable<_Fn&, iter_reference_t<_Iter>>
&& invocable<_Fn&, iter_common_reference_t<_Iter>>
&& common_reference_with<invoke_result_t<_Fn&, iter_value_t<_Iter>&>,
invoke_result_t<_Fn&, iter_reference_t<_Iter>>>;
template<typename _Fn, typename _Iter>
concept indirectly_regular_unary_invocable = readable<_Iter>
&& copy_constructible<_Fn>
&& regular_invocable<_Fn&, iter_value_t<_Iter>&>
&& regular_invocable<_Fn&, iter_reference_t<_Iter>>
&& regular_invocable<_Fn&, iter_common_reference_t<_Iter>>
&& common_reference_with<invoke_result_t<_Fn&, iter_value_t<_Iter>&>,
invoke_result_t<_Fn&, iter_reference_t<_Iter>>>;
template<typename _Fn, typename _Iter>
concept indirect_unary_predicate = readable<_Iter>
&& copy_constructible<_Fn> && predicate<_Fn&, iter_value_t<_Iter>&>
&& predicate<_Fn&, iter_reference_t<_Iter>>
&& predicate<_Fn&, iter_common_reference_t<_Iter>>;
template<typename _Fn, typename _I1, typename _I2 = _I1>
concept indirect_relation = readable<_I1> && readable<_I2>
&& copy_constructible<_Fn>
&& relation<_Fn&, iter_value_t<_I1>&, iter_value_t<_I2>&>
&& relation<_Fn&, iter_value_t<_I1>&, iter_reference_t<_I2>>
&& relation<_Fn&, iter_reference_t<_I1>, iter_value_t<_I2>&>
&& relation<_Fn&, iter_reference_t<_I1>, iter_reference_t<_I2>>
&& relation<_Fn&, iter_common_reference_t<_I1>,
iter_common_reference_t<_I2>>;
template<typename _Fn, typename _I1, typename _I2 = _I1>
concept indirect_strict_weak_order = readable<_I1> && readable<_I2>
&& copy_constructible<_Fn>
&& strict_weak_order<_Fn&, iter_value_t<_I1>&, iter_value_t<_I2>&>
&& strict_weak_order<_Fn&, iter_value_t<_I1>&, iter_reference_t<_I2>>
&& strict_weak_order<_Fn&, iter_reference_t<_I1>, iter_value_t<_I2>&>
&& strict_weak_order<_Fn&, iter_reference_t<_I1>, iter_reference_t<_I2>>
&& strict_weak_order<_Fn&, iter_common_reference_t<_I1>,
iter_common_reference_t<_I2>>;
template<typename _Fn, typename... _Is>
using indirect_result_t = typename
__detail::__indirect_result<_Fn, iter_reference_t<_Is>...>::type;
/// [projected], projected
template<readable _Iter, indirectly_regular_unary_invocable<_Iter> _Proj>
struct projected
{
using value_type = remove_cvref_t<indirect_result_t<_Proj&, _Iter>>;
indirect_result_t<_Proj&, _Iter> operator*() const; // not defined
};
template<weakly_incrementable _Iter, typename _Proj>
struct incrementable_traits<projected<_Iter, _Proj>>
{ using difference_type = iter_difference_t<_Iter>; };
// [alg.req], common algorithm requirements
/// [alg.req.ind.move], concept `indirectly_movable`
template<typename _In, typename _Out>
concept indirectly_movable = readable<_In>
&& writable<_Out, iter_rvalue_reference_t<_In>>;
template<typename _In, typename _Out>
concept indirectly_movable_storable = indirectly_movable<_In, _Out>
&& writable<_Out, iter_value_t<_In>> && movable<iter_value_t<_In>>
&& constructible_from<iter_value_t<_In>, iter_rvalue_reference_t<_In>>
&& assignable_from<iter_value_t<_In>&, iter_rvalue_reference_t<_In>>;
/// [alg.req.ind.copy], concept `indirectly_copyable`
template<typename _In, typename _Out>
concept indirectly_copyable = readable<_In>
&& writable<_Out, iter_reference_t<_In>>;
template<typename _In, typename _Out>
concept indirectly_copyable_storable = indirectly_copyable<_In, _Out>
&& writable<_Out, const iter_value_t<_In>&>
&& copyable<iter_value_t<_In>>
&& constructible_from<iter_value_t<_In>, iter_reference_t<_In>>
&& assignable_from<iter_value_t<_In>&, iter_reference_t<_In>>;
namespace ranges
{
namespace __cust_iswap
{
template<typename _It1, typename _It2>
void iter_swap(_It1&, _It2&) = delete;
template<typename _Tp, typename _Up>
concept __adl_iswap
= (std::__detail::__class_or_enum<remove_reference_t<_Tp>>
|| std::__detail::__class_or_enum<remove_reference_t<_Up>>)
&& requires(_Tp&& __t, _Up&& __u) {
iter_swap(static_cast<_Tp&&>(__t), static_cast<_Up&&>(__u));
};
template<typename _Xp, typename _Yp>
constexpr iter_value_t<remove_reference_t<_Xp>>
__iter_exchange_move(_Xp&& __x, _Yp&& __y)
noexcept(noexcept(iter_value_t<remove_reference_t<_Xp>>(iter_move(__x)))
&& noexcept(*__x = iter_move(__y)))
{
iter_value_t<remove_reference_t<_Xp>> __old_value(iter_move(__x));
*__x = iter_move(__y);
return __old_value;
}
struct _IterSwap
{
private:
template<typename _Tp, typename _Up>
static constexpr bool
_S_noexcept()
{
if constexpr (__adl_iswap<_Tp, _Up>)
return noexcept(iter_swap(std::declval<_Tp>(),
std::declval<_Up>()));
else if constexpr (readable<_Tp> && readable<_Up>
&& swappable_with<iter_reference_t<_Tp>, iter_reference_t<_Up>>)
return noexcept(ranges::swap(*std::declval<_Tp>(),
*std::declval<_Up>()));
else
return noexcept(*std::declval<_Tp>()
= __iter_exchange_move(std::declval<_Up>(),
std::declval<_Tp>()));
}
public:
template<typename _Tp, typename _Up>
requires __adl_iswap<_Tp, _Up>
|| (readable<_Tp> && readable<_Up>
&& swappable_with<iter_reference_t<_Tp>, iter_reference_t<_Up>>)
|| (indirectly_movable_storable<_Tp, _Up>
&& indirectly_movable_storable<_Up, _Tp>)
constexpr void
operator()(_Tp&& __e1, _Up&& __e2) const
noexcept(_S_noexcept<_Tp, _Up>())
{
if constexpr (__adl_iswap<_Tp, _Up>)
iter_swap(static_cast<_Tp&&>(__e1), static_cast<_Up&&>(__e2));
else if constexpr (readable<_Tp> && readable<_Up>
&& swappable_with<iter_reference_t<_Tp>, iter_reference_t<_Up>>)
ranges::swap(*__e1, *__e2);
else
*__e1 = __iter_exchange_move(__e2, __e1);
}
};
} // namespace __cust_iswap
inline namespace __cust
{
inline constexpr __cust_iswap::_IterSwap iter_swap{};
} // inline namespace __cust
} // namespace ranges
/// [alg.req.ind.swap], concept `indirectly_swappable`
template<typename _I1, typename _I2 = _I1>
concept indirectly_swappable = readable<_I1> && readable<_I2>
&& requires(_I1& __i1, _I2& __i2)
{
ranges::iter_swap(__i1, __i1);
ranges::iter_swap(__i2, __i2);
ranges::iter_swap(__i1, __i2);
ranges::iter_swap(__i2, __i1);
};
/// [alg.req.ind.cmp], concept `indirectly_comparable`
template<typename _I1, typename _I2, typename _Rel, typename _P1 = identity,
typename _P2 = identity>
concept indirectly_comparable
= indirect_relation<_Rel, projected<_I1, _P1>, projected<_I2, _P2>>;
/// [alg.req.permutable], concept `permutable`
template<typename _Iter>
concept permutable = forward_iterator<_Iter>
&& indirectly_movable_storable<_Iter, _Iter>
&& indirectly_swappable<_Iter, _Iter>;
/// [alg.req.mergeable], concept `mergeable`
template<typename _I1, typename _I2, typename _Out,
typename _Rel = ranges::less, typename _P1 = identity,
typename _P2 = identity>
concept mergeable = input_iterator<_I1> && input_iterator<_I2>
&& weakly_incrementable<_Out> && indirectly_copyable<_I1, _Out>
&& indirectly_copyable<_I2, _Out>
&& indirect_strict_weak_order<_Rel, projected<_I1, _P1>,
projected<_I2, _P2>>;
/// [alg.req.sortable], concept `sortable`
template<typename _Iter, typename _Rel = ranges::less,
typename _Proj = identity>
concept sortable = permutable<_Iter>
&& indirect_strict_weak_order<_Rel, projected<_Iter, _Proj>>;
struct unreachable_sentinel_t
{
template<weakly_incrementable _It>
friend constexpr bool
operator==(unreachable_sentinel_t, const _It&) noexcept
{ return false; }
};
inline constexpr unreachable_sentinel_t unreachable_sentinel{};
struct default_sentinel_t { };
inline constexpr default_sentinel_t default_sentinel{};
_GLIBCXX_END_NAMESPACE_VERSION
} // namespace std
#endif // C++20 library concepts
#endif // _ITERATOR_CONCEPTS_H
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